This invention was made with government support under a restricted contract. The government has certain rights in this invention.
1. Technical Field
The present invention generally relates to optical waveguides and, more particularly, to an optical waveguide incorporating a two-dimensional Bragg grating buried therein.
2. Discussion
Laser diodes are used in a myriad of modem applications such as communications, spectroscopy, solid state fiber lasers, fiber lasers, amplifiers, and the like. Some desirable laser diode properties for many applications are reliability, low-noise, single frequency, single spatial mode, and high optical powers.
The facets of a semiconductor laser degrade catastrophically when the optical power density at the facet reaches a critical value. Thus increasing the facet area is attractive for increasing the power output of these devices. However, large area devices fabricated using conventional processes tend to be multi-spatial mode due to the strict tolerances placed on the device dimensions. Also, conventional lasers and optical amplifiers are noisy since there are many modes available for amplified spontaneous emission.
In view of the foregoing, it would be desirable to provide a technique for increasing the area of the facet while maintaining a single mode output from the semiconductor laser.
The above and other objects are provided by a planar waveguide laser having a two-dimensional optical wavelength Bragg grating embedded within the guiding medium. More particularly, the waveguide preferably includes an active region sandwiched between n-doped and p-doped cladding layers. A two-dimensional Bragg grating is formed at the interface of the active region and one of the claddings. Upper and lower electrodes are defined on opposite sides of the cladding layers to complete the laser diode structure. As such, the two-dimensional grating structure provides frequency selective feedback for mode control simultaneously in both the longitudinal and lateral directions. Thus, this invention provides a technique for making a laser that emits into a large and single spatial mode at a single frequency.